Improve performance of glob pattern matching

[ChrisNeedham24]

Currently, glob pattern matching is quite a bit slower than the regex matching that dust provides - it takes almost 3 times as long, as the benchmarks show. There must be a way to improve this performance - the first thing that comes to mind is building the GlobMatcher once rather than on every call to handle_directory().

[ChrisNeedham24]

Acceptance Criteria:

• Improve performance of glob pattern matching to a maximum of double the length of dust's regex matching.
• Build the GlobMatcher only once rather than every time handle_directory() is called.